The basic principle of a solar dryer is that air is heated by
the Sun in a collector and then passed over the produce, which is to be dried.
Many fruits can be dried in Solar Dryers that use the Sun's heat to evaporate
the moisture in food items. When the moisture content is low, the food does not
rot or go bad. this way we can preserve food and use it for a long time. In the
Solar Fruit Dryer, you can dry fruits, such as grapes, quite easily. And they
taste especially good. If fresh grapes are Rs. 20 a kilo in season, and dried
grapes are Rs. 200 a kilo, which is a better buy?
You will need
Find the Right Box
Find a box with dimension that will leave about 20 cm in
front when a 45o angle is made from the top corner. Cut a section out
of the box as shown. The entire inside of the box needs to be black. You can
glue black poster paper to the inside with fevicol. If you choose to paint it,
first brush on a coat of shellac, let it dry for 5-7 hours, then paint it with a
black enamel paint.
Prepare the Box
Cut a door in the back of the box large enough to let your
hand through, plus whatever you will be putting in to dry. Reinforce the uncut,
hinging part of the door with a piece of duct tape. Poke holes in the bottom and
sides, as shown, with a sharp pencil (about 30 holes). Evaporated moisture will
be ventilated out through these holes.
Make the Screen Support
Make 3 or 4 screen support wires out of a thick wire such as
a coat hanger wire, and stick them through the box near the bottom as shown and
bend down the ends.
The Nylon Screen
Get some nylon fly screen material or mosquito netting and
cut it larger than the bottom of the box, so that the edge can be turned up and
laced to the sides of the box.
Glazing the Dryer Box
Use "Clear Vinyl Wrap" to cover the open top of the
box. Fasten the edges down securely with tape. Make two legs out of cardboard
and fasten them to the bottom with duct tape as shown. If you are worried that
insects may get in, cover the vent holes with more nylon screen and fasten it
with tape.
Source
Energy Play,
Urjapatra,
Gujarat Energy
Development Agency.
